Smoking articles, particularly cigarettes, generally comprise a tobacco rod of shredded tobacco (also referred to as cut filler) surrounded by a paper wrapper, and a cylindrical filter aligned in an end-to-end relationship with the tobacco rod. The tobacco rod is generally about 6.0 and 10.0 millimeters in diameter and 40 millimeters and 125 millimeters in length. Typically, the filter includes a segment of cellulose acetate tow attached to the tobacco rod by tipping paper. Ventilation of mainstream smoke can be achieved with a row or rows of perforations about a location along the filter.
In a conventional cigarette, the total particulate matter (TPM) per puff increases as one progresses along the puff count, i.e. the last puff may deliver twice as much TPM than the first puff. It is believed that the increase occurs because (a) as the tobacco column is consumed, the filtration caused by the tobacco shreds decreases and (b) the TPM that condenses on the shredded tobacco from earlier puffs is vaporized and combusted as the tobacco rod is consumed in subsequent puffs.